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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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GLACIERS OF HARRIMAN FIORD AND PORT WELLS          333
beneath the glacier, the larger one being about 600 feet long. These ledges, seen by Grant and Higgins in 1909 but not in 1905, increased in area from 1909 to 1910, when the glacier seemed to be descending steeply over them. They may mark the head of the fiord.
From this point eastward to Cataract Glacier in 1899 the ice surface was rather flat, and Gilbert noted that it terminated in a lofty cliff.
Barren Zone. A bare zone, whose area increased from 1899 to 1909, as noted by Grant and Higgins, extends eastward on each fiord wall as far as Cataract Glacier and marks the 1899 position of Surprise Glacier. Its upper boundary ascends rapidly westward and in 1910 attained a width of from 300 to 500 feet. Within this barren zone there was almost no vegetation; but there are extensive bare rock slopes on which vegetation will start slowly. The presence of a barren area 150 to 300 feet wide above the present surface of the Surprise Glacier on both sides shows that during the retreat of about 1J miles the glacier has also diminished notably in width and thickness.
Detached Glacier. Detached and Cataract Glaciers are cascading tongues formerly tributaries of Surprise Glacier from the north and south respectively. Detached Glacier descends from a cirque on Mt. Muir. It is about l£ miles long, 3500 feet wide, and has a projecting terminus about 1200 feet wide, which descends on the fiord wall to within a quarter of a mile of the sea, terminating 1338 feet above sea level (Fig. 47). Several streams from various points along the terminus of Detached Glacier, (PI. CXXXTV) descend the fiord wall in deep-cut gorges. In 1910 there was a moderate sized barren zone around the terminus, across which ice fragments from the glacier occasionally rolled, falling into the alder thickets and into one of the deep gullies below.
The glacier changed very little, if any, between 1899 and 1910, and Gannett's map and several 1899 photographs show that it was already detached from the Surprise Glacier, which at that time extended down the fiord beyond the terminus of Detached Glacier.
Cataract GlacieróCascading Terminus. Cataract Glacier, which is a mile and a half long and 1100 to 1600 feet wide (Fig. 47), differs from Detached Glacier in still descending the fiord wall to sea level. This is because it occupies a northern slope where melting is minimized and because it has considerably larger snowfields than Detached Glacier. Only its cascading terminus is plainly visible from the fiord and above its hanging valley lip we have not studied it. At the 1860 foot level a northern lobe about 1200 feet in length and 200 to 300 feet in width projects from Cataract Glacier, terminating 1254 feet above the fiord. Several slender streams, with foaming cascades, descend the fiord wall from this terminus.
Cataract Glacier is the only cascading glacier in Harriman Fiord which is now active enough to descend the fiord wall to the sea, as so many slightly-larger cascading glaciers do in College Fiord. The glacier emerges from its hanging valley at about the 2000 foot level, descends the fiord wall (PI. CXXXV) at the rate of 2850 feet per mile and terminates in a vertical cliff 50 feet or more in height, which rises out of such, shallow water that there is practically no undercutting by the sea. Therefore the icebergs from Cataract Glacier are both small and few in number. Most of the glacier surface is severely crevassed, but the eastern edge has a low, sloping terminus, more or less mantled with ablation moraine, over which it is easy to walk. The end of the glacier divides over a low, striated, rock spur.
Advance.   Cataract Glacier was beginning to advance in 1910, after having remained